Lung tissue is composed of two basic types of structures, i.e. vascular networks to carry blood, and bronchial structures that carry air to oxygenate the blood. Resection of this type of tissue poses two problems to a surgeon. The first problem is achieving hemostasis of the vascular networks. The second problem is achieving pneumostasis of the bronchial structures. Additionally, since these procedures usually involve lung tissue that is frequently diseased, the diseased lung tissue is often overdistended, or inflamed, thus resulting in thin, fragile, friable tissue.
Consequently, a variety of techniques are available to surgeons as a means of controlling hemostasis and pneumostasis in lung tissue. The techniques include suturing, the application of clips, stapling, the application of RF energy, and the use of other energy modalities. A common surgical procedure is the resection of a portion of the lung as a means to remove a tumor, or as a means to reduce the lung volume in emphysemic patients.
Lung volume reduction surgery is performed on patients with emphysema wherein some of the air sacs within the lungs become overdistended or inflamed, resulting in destruction of alveolar walls. The size of the thoracic cavity is fixed, and when the diseased tissue swells, it compresses the healthy lung tissue thereby reducing the volume of air that can be ingested into the healthy portions of the lungs. This results in shortness of breath, painful breathing, and eventually could lead to right ventricular hypertrophy and heart failure.
The primary cause of emphysema is smoking, and the damaged tissue is generally confined to the upper lobes of the lungs. As a means of increasing the volumetric efficiency of the lungs, lung volume reduction surgery was developed. In this surgery, damaged portions of the lungs are removed, reducing the constricting effects caused by overdistended diseased tissue. Although the volume of the lung tissue is reduced, the elimination of diseased tissue has a dramatic beneficial effect to the patient by enabling the remaining tissue to work with increased volumetric efficiency.
Electrocautery instruments are commonly used when accessing a patient for thoracic surgery. These instruments apply monopolar or bipolar Radio Frequency (RF) energy to cauterize the "bleeders" in the chest wall as the chest cavity is being opened. Monopolar instruments have one electrode that is associated with a cutting or cauterizing instrument and a return electrode is attached to a remote portion of the patient. Hemostasis is controlled by the application of the energized device to the site of the bleeder such that the current arcs between the tip of the device and the tissue application site, thus cauterizing the bleeder.
Bipolar instruments normally apply a cauterizing current to a pair of electrodes, located within or, formed by moveable opposed jaw members of the instrument. Tissue is cauterized by placing it within the open jaw members of the instrument, closing the jaw members of the instrument upon the tissue to bring the electrodes into close proximity, and then applying RF bipolar energy to the compressed tissue within the jaw members. The current arcs between the electrodes and cauterizes, coagulates, or tissue welds the tissue compressed therein. Bipolar electrocautery has been used to resect metastic lesions in lung tissue. The procedure, using cautery forceps, was found to have a low postoperative morbidity from air leaks, but was quite lengthy. This was described in a paper by Cooper, Joel D. et al. "Precision Cautery Excision of Pulmonary Lesions", Annals of Thoracic Surgery 4:51-53, 1986.
Additionally, mechanical devices such as surgical staplers and linear cutters, both open and endoscopic, have also been utilized as a means of resecting diseased lung tissue. Staples have long been used to provide hemostasis in vascular structures, and when applied to lung tissue, were found to provide a good degree of pneumostasis as well. Surgical cutters have a plurality of staples held in multiple staggered rows in a replaceable cartridge. The cutters compress the lung tissue, and the staples are fired into the compressed tissue in close proximity to the diseased portion of the lung that is to be excised. A cutting blade is passed longitudinally between the innermost rows of formed staples, transecting the tissue. The cutter is removed from the surgical site, reloaded with another unfired stapling cartridge, and the procedure is repeated until the desired section of the lung is resected and removed.
One known problem which can arise with using surgical staplers in this fashion has been the formation of air leaks in the stapled lung tissue. The leaks can occur in the cut line, and/or in the staple holes themselves. Frequently, the diseased lung tissue is thin and friable and can tear at the staples as the lungs reinflate. These air leaks can be persistent and require additional surgery to locate and control. As one would expect, persistent leaks can extend the hospital stay for a patient by weeks.
As a means to alleviate the leakage problems outlined above, surgeons have developed a technique of averting the incised wall of giant bullae to act as a reinforcement for the staple line. The averted tissue provides additional material for the staples to be formed into, thereby reducing the chances of tearing at the staple line. It also reduces staple pullout in friable tissue, and results in improved pneumostasis. J. D Cooper et al. describes this procedure in a paper entitled "Median Sternotomy for Bilateral Resection Of Emphysematous Bullae", Journal of Thoracic Cardiovascular Surgery, Vol. 82 (1981), 892-897.
While the above technique was initially identified as a breakthrough procedure, large bullae are infrequently found within patients. This lack of available reinforcement material prompted a search by the medical community for a more easily obtainable reinforcement material. Accordingly, a variety of materials, both synthetic and natural, have been developed for use as a reinforcement material for lung resection. These materials include VICRYL.RTM. of Johnson and Johnson, New Brunswick, N.J., "DEXON.RTM., of Sherwood-Davis and Geck, St. Louis, Mo., TEFLON.RTM., of E. I. DuPont de Nemours & Co., Wilmington, Del., and animal material such as tanned bovine pericardium. These reinforcement materials are normally mounted into the jaw members of a linear cutter such that upon firing, the reinforcement material is stapled to the lung tissue. Optimally the, lung tissue is "sandwiched" between two layers of this reinforcement material. Use of the reinforcement material reinforces the staple line, reduces tissue tearing, and acts as a sealing material. The use of these materials, along with improved methods of attachment are disclosed in U. S. Pat. No. 5,397,324 by Carroll et al., and U.S. Pat. Nos. 5,503,638; 5,549,628; and 5,575,803 by Cooper et al.
Although the use of an easily obtainable, easily applicable reinforcement material is a great improvement in lung surgery, there is still reluctance by the surgical community to embrace these techniques. One reason is increased surgical procedure time. Another reason is the substantial cost involved in using the reinforcement materials such as those described above. Accordingly, up until now, there is no known method of lung resection surgery that can reduce the operating time, provide improved hemostasis and pneumostasis and eliminate the need to utilize a separate reinforcement.